Coated rolling mill roll



N 3, 1936. J. E. MONTGOMERY El AL 2,059,384

' COATED ROLLING MILL ROLL Filed Dec. 29, 1935 Patented Nov. 3, 1936 UNITED STATES PATENT OFFICE COATED ROLLING MILL ROLL Application December 29, 1933, Serial No. 704,504

2 Claims.

This invention relates to rolls adapted for use in rolling metal shapes and particularly for use in rolling steel shapes. The manufacture of metal shapes is highly developed'and it is the established practice in the shaping of metal products, such as strip, sheets or other shapes, to effect a reduction in the thickness of the stock by passing stock between a pair of revolving rolls which are so spaced that the distance between them is somewhat less than the thickness of a section of stock entering the rolls. The rolls compress the stock, causing it to be reduced in section and increased in length.

The pressure exerted on the rolls, particularly in cold rolling steel is enormous and great difficulty has been experienced in securing rolls which are ductile to withstand the shock produced as the piece of stock enters the rolls; strong, to resist the pressure applied to the bearings at the ends of the rolls; hard, to give them good wearing qualities; sound, so that they may not develop surface defects which would leave their marks on the surface of every piece rolled by them and causing the material to be rejected; and free from internal stresses so that the roll will not crack or fracture as a result of expansion and contraction in response to temperature changes.

Two kinds of rolls are now in general use, these being chilled rolls and forged rolls, the chilled rolls usually being a cast iron roll having a chilled surface, the depth of the chill ranging from between land 3 inches, while forged rolls are constructed of forged steel and are heat treated to give them the required surface hardne'ss. Forged steel rolls have been found to be the most satisfactory and are the only ones which are employed for finishing operations. However, forged rolls are not entirely satisfactory as the rolls soften after use and must be removed from the stand or mill and be reconditioned in order to restore the original hardness and finish. The reconditioning process is expensive as the mill must be shut down when the roll is to be removed, and in addition, the roll may crack when it is heated during the reconditioning process and thereby be rendered worthless.

It has also been found that forged rolls having a high surface hardness frequently have internal' stresses which result either in cracking or fracturing of the roll, or spalling, that is, chipping out or splitting off of fragments of metal from the face of the roll thereby rendering the roll worthless. The principal object of the present invention is to provide a roll adapted to be employed in the manufacture of metal shapes and having a surface hardness beyond that which it is possible to secure under the present methods of making rolls.

Another object of the invention is to provide an improved roll having a smoother finish than the rolls now in use.

A further object of the invention is to provide a roll capable of being operated at a higher speed than the rolls now in use. 10

Another object of the invention is to provide an improved roll having an increased working life.

A further object of the invention is to provide a roll having improved bearing surfaces. 15

Other objects of the invention and features of novelty will be apparent from the following description taken in connection with accompanying drawing, in which Fig. 1 is an elevational view of a roll embodying our invention.

Fig. 2 is an end view of the roll shown in Fig. 1.

Fig. 3 is an enlarged fragmentary sectional view taken substantially along the line 3-3 of Fig. 1, the plating on the roll being shown greatly increased in thickness for purposes of illustration, and the surface of the plating before grinding being indicated by a broken line.

Referring to the drawing, we have shown-one form of roll embodying our invention and the roll therein illustrated has a cylindrical body indicated by the reference character I, which is the working area or zone acting upon the material to be rolled, through its outer surface coating 5. The necks or the parts which rest on the bearings supporting the ends of the roll, are indicated by the reference characters 2 and 3. The roll is also provided with wobblers indicated by reference'character 4, which are formed by notching the prolongation of one of the necks and which provide means by which the roll may be driven. The body may vary in diameter from a few inches to several feet and may also vary in length, from a'few inches to several feet, such as for example 15 to 20 feet.

The roll provided by our invention may be constructed of chilled cast iron or forged steel as at present, or may be constructed of any other material of suitable density and physical strength. The roll body should have a relatively high degree of hardness, but it is not necessary that the surface of the roll itself be as hard as in rolls heretofore employed.

In the manufacture of the improved roll provided by our invention, the rough roll, either chill cast or forged, is placed in a grinding machine and the body and the necks or journals are ground and lapped to secure a smooth straight surface. The roll is then removed and is washed and cleaned and is then immersed in a bath of platin solution, and the surface of the body of the roll and the surface of the necks or journals are plated with a suitable metallic covering such as chromium or other hard metal, the plating on the face of the body of the roll being indicated, as stated, by the reference numeral 5 and the plating on the bearing surfaceson the necks 2 and 3 being indicated by the reference numerals 6 and 1. The plating on the face of the body of the roll preferably extends the entire axial distance thereof, as between the broken lines shown in Fig. 1 of the drawing, while the plating on the necks or journals extends substantially the entire length of these portions, as between the broken lines adjacent these portions on the drawing. The roll may be revolved either periodically or continuously during the plating process, in order to insure that the coating will be of uniform thickness over the entire face of the roll.

.When the plating is completed the roll is removed from the bath and placed in a grinding machine, where the surface of the plating on the body of the roll is ground and lapped.

While the invention is not limited to any particular thickness of plating, it has been found that a coating .011 of an inch thick before grinding and lapping is satisfactory.

We have found that a metallic coating applied in this way adheres to the body of the roll and that the plating will not flake or peel off even when the roll is subjected to the pressures which must be employed in the cold rolling of steel.

It has been found that by plating the face of the body of the roll, it is possible to secure an increase in the hardness of the face of the roll ranging from 20 to 40% above the hardness of the unplated body of the roll. In addition it has been found that the plated roll has a much longer life than the unplated roll and produces better finish on the surface of the rolled material, and that because of the increased hardness and smoother finish on the face of the roll there is less friction between the roll 'and material being rolled and therefore less heat is generated, and that as a result the plated rolls can be operated at substantially higher speeds than the unplated rolls heretofore in use.

It has been found also that as the body of the roll does not need to have as great a surface hardness before plating as was required for the unplated rolls, that the rolls have fewer internal stresses, and that there is less danger of fracture or cracking of the rolls than heretofore.

. Because of the increase in the hardness of the final outer surface of the roll secured by this process, the roll has a much longer life and fewer changes in rolls are required. When the face or body of the roll requires reconditioning, the roll may be restored to its original condition merely by replating, grinding and lapping the face of the body of the roll. It is unnecessary to heat treat the roll with possible result of fracturing or cracking it.

The improved roll provided by this invention has the necks or journals plated with the same material found on the face of the body of the roll and it has been found that by plating and polishing the necks or journals the life of these parts is increased greatly, and that there is substantial reduction in the friction in the roll neck bearings, with a corresponding reduction in the heat generated in the bearings and in the wear on the necks or journals and the bearing block s. This reduces the amount of lubricating oils required, and reduces the power required to turn the roll, and facilitates cooling. It has been found also that the plated journals or necks do not score and hence have a much longer life than the unplated surfaces. Also, as the wear on the bearings is greatly reduced or practically eliminated, the plated rolls are held in accurate alignment with the result that the rolls produce a better finished product.

While one embodiment of the roll provided by our invention has been described and illustrated in detail, it should be understood that the in-' vention is not limited to these details but that numerous modifications and changes may be made without departing from the spirit and scope of the appended claims.

We claim:

1. A roll adapted to be employed in the rolling of metal shapes and having a substantially predetermined degree of composite hardness, the roll comprising a metallic body heat treated to increase the hardness of its peripheral surface to adegree not causing cracking or spalling, wherefore said peripheral surface is left at a lower degree of hardness than said predetermined degree of composite hardness, said peripheral surface having thereon a coating of metal of a hardness higher than said predetermined degree of composite hardness, said coating comprising a layer of chromium applied to the surface of said body by electroplating.

2. A method of manufacturing rolls for rolling metallic shapes, said rolls having a working area extending longitudinally and around the periphery thereof, said working area having a predetermined degree of composite hardness, comprising heat treating acyIindrical body to produce on the peripheral surface a predetermined degree of hardness, said hardness being less than that which would cause cracking or spalling, and then coating said surface with a deposit of metal having a higher-degree of hardness than said predetermined degree of composite hardness.

JULIAN EARL MONTGOMERY. PAUL EDWARD JONES. 

